Turbochargers may be used in an engine system to increase a pressure of air supplied to the engine for combustion. In one example, the turbocharger includes a turbine coupled in an exhaust passage of the engine which at least partially drives a compressor via a shaft to increase the intake air pressure. High pressure air from the turbine or the compressor may leak past non-contact labyrinth seals into an oil cavity surrounding the shaft of the turbocharger. Because the low pressure oil cavity is in fluid communication with a crankcase of the engine, crankcase pressure may increase due to the leakage of the high pressure air, leading to crankcase over pressure events and eventual removal of the turbocharger from the engine system, for servicing or replacement.
In other examples, crankcase over pressure events may occur due to other factors, such as degradation of piston rings, which increases blow-by around the piston, and/or degradation of an evacuation system which maintains a pressure of the crankcase. In such examples, however, the turbocharger may still be removed from the engine system even though it is not the cause of the crankcase over pressure event, if the exact cause of the crankcase overpressure event is unknown.